Optical codes are patterns made up of image areas having different light reflective or light emissive properties, which are typically assembled in accordance with a priori rules. The term “bar code symbol” is sometimes used to describe certain kinds of optical codes. The optical properties and patterns of optical codes are selected to distinguish them in appearance from the background environments in which they are used. Devices for identifying or extracting data from optical codes are sometimes referred to as “optical code readers” of which bar code scanners are one type. Optical code readers are used in both fixed or portable installations in many diverse environments such as in stores for check-out services, in manufacturing locations for work flow and inventory control, and in transport vehicles for tracking package handling. The optical code can be used as a rapid, generalized means of data entry, for example, by reading a target bar code from a printed listing of many bar codes. In some uses, the optical code reader is connected to a portable data processing device or a data collection and transmission device. Frequently, the optical code reader includes a handheld sensor that is manually directed at a target code.
Most scanning systems, or scanners, generate a beam of light which reflects off a bar code symbol so the scanning system can receive the reflected light. The system then transforms that reflected light into electrical signals, digitizes the signals into a digital bar pattern (DBP) signal, and decodes the DBP signal to extract the information embedded in the bar code symbol. Scanning systems of this type are described in U.S. Pat. Nos. 4,251,798; 4,360,798; 4,369,361; 4,387,297; 4,409,470; and 4,460,120, all of which have been assigned to Symbol Technologies, Inc.
In recent years, enhanced signal processing techniques have been developed for integrated scanners and decoded scan engines. The enhanced signal processing techniques convey transition strength information in addition to the basic transition timing information that is provided by traditional signal digitizers. For example, multibit digitized signals are described in U.S. Pat. No. 5,302,813 to Goren, assigned to Symbol Technologies, Inc. and incorporated herein by reference in its entirety. While these scanner signals provide more detailed information about the analog signal being received by the detector, they require more complex interfaces between the digitizer and the decoder.